1. Field of the Invention
This invention relates generally to polishing tools and more particularly, an orbiting polishing tool for at least one of polishing and material removal from a target hole.
2. Description of Related Art
In a process of performing modifications or making repairs to internal components of a nuclear reactor, a machining of existing structures to remove remnants of removed components is often performed. One process for performing this machining is Electrical Discharge Machining (EDM). The EDM method utilizes an electrical current passed from an electrode to a target work piece base metal from which remnants are to be removed. This process leaves behind a thin recast layer on the machined work piece surface consisting of re-solidified base metal and electrode residue. This recast layer is extremely hard, rough, and may present undesirable micro-cracks, which extend into a base metal of the work piece. It is often necessary, in particular when the base metal of the work piece includes an Inconel alloy, to remove the recast layer and the attendant micro-cracks.
In the past, the recast layer has been removed by honing or by aggressive polishing with a suitable abrasive. Recast layer removal by conventional honing has been applied to both vertical and horizontal holes. Recast layer removal in a nuclear reactor environment typically requires tooling of significant power, robust construction, complex motions and actuations, and precise locating when installed. Cutting media of recast layer removal systems typically includes discrete stones with a complex mounting head capable of supporting the stones and accommodating the significant mechanical loads.
As the hole diameter of a work piece increases above approximately 3.00 inches, it may become more difficult, especially with horizontal centerline holes, to implement a hone given the space and accessibility constraints within the reactor. Additionally, the honing process requires a subsequent metallurgical examination of the surface to demonstrate that honing operation did in fact produce an acceptable surface condition. Recast layer removal by aggressive polishing has been implemented to remove as much as 0.050 diametrical inches for larger sized vertical centerline holes. The recast layer removal tooling typically features mechanisms that spatially position the polishing media, hold the tooling against the work piece surface, and provide the power necessary to rotate the media. In general, part of the motion required to polish a surface of the work piece is provided via a manual interface.